Slow cookoff of solid propellant was experimentally studied at the University of Illinois by examining the behavior throughout the cookoff process. The general concept involved preparing axial-symmetric samples of chosen compositions and casting them into carbon fiber cases. The cured samples were then placed inside the test apparatus to slowly heat until auto-ignition while continuously recording data used to help validate a complex thermal-chemical-mechanical code being built to model the cookoff behavior of energetic materials.
Preliminary work focused on developing the test apparatus and successful implementation of all diagnostics. Experimental data taken for the scope of this research included three thermocouple readings of varying radius for spatial temperature gradients, pressure and spectrometry measurements on decomposition and combustion gases, and images of the surface of the carbon fiber case used in digital image correlation to yield mechanical displacement.
Single base ammonium nitrate propellant was the first propellant composition used in developing the test apparatus. Following successful implementation and testing of the diagnostics, a series of tests were conducted to establish repeatability of all developed methods and procedures. For these tests, a common ammonium perchlorate composition previously used was duplicated to compare the data. After successful repeatability tests, single-base propellants were tested in accordance with slow cookoff standards. The development of the test apparatus, results of all tests, and current status of all diagnostics are discussed in detail.